1. Field of the Invention
The present invention relates to a liquid crystal display (LCD) device, and particularly, to an LCD device having a backlight assembly capable of preventing light leakage.
2. Background of the Invention
Generally, a Flat Panel Display (FPD) is applied not only to monitors of desk top computers, but also to small and light systems including portable computers such as notebooks and personal digital assistants (PDA), or portable phones. This FPD includes a liquid crystal display (LCD) device, a plasma display panel (PDP), a field emission display (FED) device, etc. Among these FPDs, the LCD device is being widely applied to portable phones, computer monitors, televisions, etc. due to an excellent viewing characteristic, average power consumption less than that of a cathode ray tube (CRT), and a small heating value.
The LCD device is a non-emissive type display device for displaying an image by controlling the amount of light incident thereon from an external optical source. Accordingly, the LCD device requires a backlight assembly including an additional optical source for irradiating light to an LC panel.
The backlight assembly includes an LED device serving as an optical source, a light guide plate coupled to a light emission surface of the LED device, and a plurality of optical sheets disposed on the light guide plate.
The conventional LCD device having the backlight assembly will be explained in more detail with reference to FIGS. 1 and 2.
FIG. 1 is a sectional view schematically showing a liquid crystal display (LCD) device having a backlight assembly in accordance with the conventional art, and FIG. 2 is an enlarged sectional view schematically showing a state that light leakage occurs from a light leakage portion disposed between a light guide plate and a light emitting diode (LED) printed circuit board (PCB) in the LCD device having a backlight assembly in accordance with the conventional art.
Referring to FIG. 1, the conventional LCD device comprises a display assembly (not shown), a backlight assembly (not shown) for providing light to the display assembly, and an accommodation member (a lower frame) 35 for accommodating therein the display assembly and the backlight assembly and fixing them.
Referring to FIG. 1, the display assembly includes an LC panel 10, a LCD Driver IC (not shown) mounted at one side of the LC panel 10, and a Flexible Printed Circuit Board (FPCB, not shown) having one end connected to the LC panel 10.
The LC panel 10 includes a color filter (CF) substrate 13, and a thin film transistor (TFT) substrate 11 disposed below the CF substrate 13.
Referring to FIG. 1, the backlight assembly includes an optical source 15, a light guide plate 17 coupled to the optical source 15, a reflector 25 disposed below the light guide plate 17, an optical sheet 20 disposed on the light guide plate 17, and a mold frame 23 for accommodating therein the optical source 15, the light guide plate 17, the reflector 25 and the optical sheet 20.
The optical source 15 is installed on a light incidence surface of the light guide plate 17, and includes an LED device 15a and a substrate 15b having the LED device 15a mounted thereon.
The LED device 15a is a side view type device, and emits light toward side surfaces of the light guide plate 17.
The light guide plate 17 is coupled to one side of the optical source 15, i.e., a light emission surface of the LED device 15a, and converts a point optical source or a linear optical source into a planar optical source.
Accordingly, light emitted from the LED device 15a is made to be incident onto one surface of the light guide plate 17 adjacent to the LED device 15a. And, the light incident onto the light guide plate 17 is converted into a planar optical source, and is made to be incident onto the LC panel 10.
The reflector 25 is disposed below the light guide plate 17, and reflects a part of light emitted to a lower side of the light guide plate 17, to the light emission surface of the backlight assembly thereby to enhance optical efficiency. And, the reflector 25 controls reflectivity of entire incident light, thereby implementing uniform brightness on the entire surface of the light emission surface.
The optical sheet 20 consists of a diffusion plate 19, and one or more prism sheets 21. And, the optical sheet 20 is disposed on the light guide plate 17, and allows light emitted from the light guide plate 17 to have uniform brightness.
The mold frame 23 is formed in a quadrangular frame shape having opened upper and lower surfaces, and accommodates therein the backlight assembly and the LC panel 10, sequentially.
An LED FPCB (Flexible Printed Circuit Board) 31 is attached onto the mold frame 23 and the optical source 15 by a first double-sided tape 29. As shown in FIG. 2, a part 33 of light emitted from the optical source 15 leaks onto side surfaces of the optical sheet 20 through light leakage portions 37 disposed between the double-sided tapes 29 attached between the LED FPCB 31 and the light guide plate 17.
The LC panel 10 is mounted on the mold frame 23 and the LED FPCB 31, and a second double-sided tape 27 is disposed between the LC panel 10 and the mold frame 23. The second double-sided tape 27 serves to fix the LC panel 10 to the mold frame 23.
The lower frame 35 is formed in a rectangular box shape having an opened upper surface, and fixes components of the LC panel 10 and the backlight assembly accommodated in the mold frame 23. Accordingly the lower frame 35 having the LC panel 10 and the backlight assembly accommodated therein is coupled to a top chassis (not shown), thereby constituting the LCD device.
However, the conventional LCD device has the following problems.
Firstly, light emitted from the optical source leaks onto the side surfaces of the optical sheet through the light leakage portions disposed between the double-sided tapes 29 attached between the LED FPCB 31 and the light guide plate 17. Especially, as light emitted from the LED has a high luminous intensity, the amount of light leakage occurring from a gap between the LED FPCB 31 and the double-sided tape increases.
This may cause the LCD device to have lowered brightness uniformity.